Wednesday, January 23, 2008

NASA images spark life on Mars speculations

REAL OR ILLUSION? The image has set the Internet abuzz that there really is life on Mars.

REAL OR ILLUSION? The image has set the Internet abuzz that there really is life on Mars.


JUST LIKE US: The NASA images show a woman-like figure.
SO FAR: An arrow points towrds the woman-like figure.

London: Life on Mars? Well, bizarre images have emerged showing a mystery female figure walking down a hill on the arid planet.

The photo of what looks like a naked woman with her arm outstretched was among several taken on the red planet and sent back to Earth by NASA's Mars explorer Spirit, the Daily Mail reported on Wednesday, citing an unnamed website.

Though no official confirmation has come from NASA whether the figure is an alien or an optical illusion caused by a landscape on Mars, it has set the Internet abuzz that there really is life on Mars.

As one enthusiast put it on the website, "These pictures are amazing. I couldn't believe my eyes when I saw what appears to be a naked alien running around on Mars."

The news of the mystery woman on Mars came just days after a team of French scientists claimed to have discovered proof that the red planet possesses high-level dense clouds of dry ice, which scud across its orange sky.

Using data obtained by the OMEGA spectrometer on board ESA's Mars Express, the team found the existence of the ice clouds which sometimes become so dense that they throw quite dark shadows on the dusty surface of the red planet.

"This is the first time that carbon dioxide ice clouds on Mars have been imaged and identified from above. This is important because the images tell us not only about their shape, but also their size and density."

"Previously, we had to rely on indirect information. However, it is very difficult to separate the signals coming from the clouds, atmosphere and surface," according to lead scientist Franck Montmessin of the Service d'Aeronomie at University of Versailles.

Saturday, January 19, 2008

Wiring diagrams

The difference between a schematic diagram and a wiring diagram is the amount of
detail included. In a schematic diagram, the interconnection of the components is
shown, but the actual values of the components are not necessarily indicated.
You might see a diagram of a two-transistor audio amplifier, for example, with resistors
and capacitors and coils and transistors, but without any data concerning the
values or ratings of the components. This is a schematic diagram, but not a true wiring
diagram. It gives the scheme for the circuit, but you can’t wire the circuit and make it
work, because there isn’t enough information.
Suppose you want to build the circuit. You go to an electronics store to get the
parts. What sizes of resistors should you buy? How about capacitors? What type of transistor
will work best? Do you need to wind the coils yourself, or can you get them ready
made? Are there test points or other special terminals that should be installed for the
benefit of the technicians who might have to repair the amplifier? How many watts
should the potentiometers be able to handle? All these things are indicated in a wiring
diagram, a jazzed-up schematic. You might have seen this kind of diagram in the back of
the instruction manual for a hi-fi amp or an FM stereo tuner or a television set. Wiring
diagrams are especially useful and necessary when you must service or repair an electronic
device.

Oscilloscopes

Another graphic meter is the oscilloscope. This measures and records quantities that
vary rapidly, at rates of hundreds, thousands, or millions of times per second. It creates
a “graph” by throwing a beam of electrons at a phosphor screen. A cathode-ray tube,
similar to the kind in a television set, is employed.
Oscilloscopes are useful for looking at the shapes of signal waveforms, and also for
measuring peak signal levels (rather than just the effective levels). An oscilloscope can
also be used to approximately measure the frequency of a waveform. The horizontal
scale of an oscilloscope shows time, and the vertical scale shows instantaneous voltage.
An oscilloscope can indirectly measure power or current, by using a known value of resistance
across the input terminals.
Technicians and engineers develop a sense of what a signal waveform should look
like, and then they can often tell, by observing the oscilloscope display, whether or not
the circuit under test is behaving the way it should. This is a subjective kind of
“measurement, “ since it is qualitative as well as quantitative. If a wave shape “looks
wrong,” it might indicate distortion in a circuit, or possibly even betray a burned-out
component someplace.